The first thing you will see upon entering the museum is this clock that is stopped at 11:02.11:02:35 am is actually the precise time the atomic bomb hit Nagasaki. /goosebumps.

The residents of Nagasaki consider it their duty to make sure the horrors which they experienced due to the atomic bombing are never repeated.[12] Because of this, the museum is designed in such a way that the audience can see just what effect the bomb had on the city, the reconstruction, and the lasting effects of the atomic bomb. The museum opens with a room dedicated to the city as it was just before the bomb decimated Nagasaki. [source]

Inside you will see various artefacts and remnants of the bombing.

The permanent exhibition rooms display large materials exposed to the blast, as well as a replica of a sidewall of the Urakami Cathedral which was hit by the bomb. [source]

Saki-san and Okagawa-san looking artefacts.

This photo exhibit / timeline gives us a glimpse of the destruction caused by the bombing.

This shows us exactly where the atomic bomb was dropped.

Several preserved clothing and artworks dedicated to the victims.

The atomic bomb was developed by scientists working under the Manhattan Project. The project was granted funding on December 6, 1941, with American leaders aiming for a new invention that would serve as a wartime weapon.[7] The decision to drop an atomic bomb on Japan had been made by 1943, and a shortlist of candidate target cities was in place in 1945. At the time, it was argued that an atomic bombing would bring about a more rapid end to the war. Hiroshima, the first target, was selected to show the power of America’s new weapon. The second bombing, of Nagasaki, was intended to demonstrate that the USA had a large arsenal.[8] At 11:02 A.M. local time on August 9, 1945, the atomic bomb, nicknamed Fat Man after Winston Churchill, was dropped on Nagasaki, forever changing the city’s landscape.[8] A mushroom cloud rose to an altitude of 45,000 feet above the city.

Doctor Takashi Nagai [永井 隆] was a physician specializing in radiology and was a survivor of the atomic bombing. He was a Roman Catholic convert and is also popularly known as the saint of Urakami. Takashi Nagai is well known for his efforts in helping the victims despite his severe injuries and the loss of his wife [due to the bomb].